How would the nurse categorize an intravenous solution of 0.45% sodium chloride?

A 0.45% sodium chloride solution is categorized as hypotonic because its osmolarity is lower than that of the body's plasma. In a hypotonic solution, the concentration of solutes (in this case, sodium chloride) is less than that found in the bloodstream, which leads to a net movement of water into cells. This can cause the cells to swell and potentially become lysed, or burst, as water moves in to equalize the solute concentration on both sides of the cell membrane.

It’s important to note that isotonic solutions have the same osmolarity as body fluids, which would be around 0.9% sodium chloride, whereas hypertonic solutions have a higher solute concentration, causing water to move out of cells and leading to cell shrinkage. Isomeric is a term that does not apply in this context, as it relates to molecules having the same formula but different structures. Thus, categorizing 0.45% sodium chloride as hypotonic accurately reflects its effects on cell volume and body fluid dynamics.